inman



G. E. INMAN Oct. 31-, 1939.

Filed Sept. 25, 1936 Fig. I.

n E a 9 Jm v m Pm e L H m m w Jw H 8 i w as vmi 0 B m 0 3 w ww/NH x U n a a 1 1 I Z 2 b i/d a H 4 W 4 n m n u u F m 4M I yn M w m w n L New Earls My invention relates to a method and apparatus for flashing electric discharge lamps to ohtain a very intense flash of light or radiant energy which may be used, for example, for photographic or for signalling purposes.

According to my invention, a discharge lamp is operated under normal conditions with a ballast in series and the ballast, or a portion thereof, is shunted momentarily to permit an abnormal amount or current to flow through the lamp to cause it to emit a flash of light of very high intensity. A time control device is preferably included in the circuit to automatically limit the abnormal operation of the lamp to a very short period so that the time of the flash is less than. about one-fifth of a second, corresponding to twelve cycles of a sixty'cycle line current. The lamp may be of the high pressure positive column metal vapor type or of the low pressure gaseous discharge type in which the light is obtained from a discharge through a gas such as neon. When the lamp is used for photographic purposes, suitable means are provided in the circuit to syn chronize the operation of the camera shutter with the hash of light. When the lamp is used for this purpose it may be operated under normal conditions to provide sufficient illumination for the photographer to focus his camera and adjust the position of his subject and then the lamp may be flashed to provide the high intensity illumination necessary for an instantaneous exposure. Other features and advantages of my invention will appear from the following detailed description of species thereof and from the drawing.

In the drawing, Fig. 1 is a diagram ot a circuit for operating a discharge lamp according to my invention including means for operating a camera shutter, and Fig. 2 is a diagram of a modified circuit.

Referring to Fig. i, the lamp it may he of the high pressure positive column metal vapor type disclosed in the United States patent application Serial No. 102,552, Eugene Lemmers, filed Septemher 25, 1936 now Patent No. 2,130,304. This particular lamp contains a filling of argon at a pressure of about 6 mm. of mercury and a quantity of vaporlzable metal ll, preferably mercury. A pair of main electrodes 12-42 are located at opposite ends of the bulb and a starting electrode i3 is preferably provided adjacent to the upper electrode ii. The said main electrodes preferably consist of highly porous slugs or blocks of refractory metal, preferably tungsten, impreg= nated with an electron emissive material such as barium oxide, as disclosed and claimed in. the

Application 35, Nor (5H, a a

United patent application Serial No. e Lenanaers et al., filed April 16, 1935 now No. 2,121,637. Such electrodes contain a very ri h; amount of electron emissive material are therefore particidarly well suited to withstand the effects of a high overload for short periods of time. ihe electrodes il -i2 are mounted on leads iG-ii which are made large enough to safely carry the momentary high current.

The circuit for normal operation of the lamp it inclu es a conductor i5 which connects the lead i l of the upper electrode E2 to one side of the line through a switch i6, and a conductor ll which connects the lead of the lower electrode it? to the other side of the line through a ballast, shown here a choke coil ill. The starting electrode i3 is connected through a high resistance 59 to the lower electrode 52. When the switch it is closed, a discharge is initiated be- M tween the upper electrode i2 and the starting electrode i3 and the gas in the bulb is ionized, thereby causing the arc to start between the two main electrodes 82-92. This lamp operates with a concentrated are at a pressure of about two atinospheres.

'ihe lamp is caused to flash at a very high intensity by a time control means, shown within the dotted lines which momentarily shunts the choke coil so that, in this case, the full line voltage is applied across the lamp id. The time control means 29 comprises a relay lit, the coil 22 and armature 23 or which are connected on one side through a conductor and one side of a double pole switchfi'd to the conductor ii, and on the other side through a conductor 26, variable resistance conductor 28, and the other side of said switch 25, to the conductor E5. A resistance, preferably in the form of an incandescent lamp iii having a tungsten filament, which has a positive temperature coefricient of resistance, is con.- nected across coil 2?! of the relay M by conclusters 3%} and 38 which are connected to the conductors 2d and respectively. The armature 23 of the relay fit is normally held against the stavhy conductors and 3? to the conductors 28 and 2d respectively. The armature 38 of the solenoid ill is arranged to actuate the control lever 39 of a camera shutter 40 so as to open said shutter when the lamp i is flashed.

To operate the device, the switch i6 is first closed to cause the lamp It! to operate normally, as explained above, with the choke coil in series to lower the line voltage and limit the current. To flash the lamp and operate the camera shutter 40, the switch 25 is closed. This action shunts out the ballasting choke coil it, the circuit then being from one side of the line through conductor l5, upper electrode E2 of lamp i0, lower electrode l2, conductor 33, contact 32, armature 23, conductor 24, and conductor ill, to the other side of the line. Since the full line voltage is then applied to the lamp, an abnormal current flows therethrough and the lamp emits light of extremely high intensity. The closing of the switch 25 also connects the coil 35 of the solenoid 34 across the line, thereby attracting the armature 38 and tripping the shutter control lever 39. The abnormal flow of current'through the lamp i0 is permitted by the time control means 23 to continue for but an extremely short time (onetwentieth of-a second, for example, with a shutter speed of one-fiftieth of a second).

The operation of the time control means 20 is as follows: When the switch 25 is closed, the coil 22 of relay 2| and the incandescent lamp 29 are also connected across the line, the circuit being from one side of the line through conductor ll, conductor 24, relay coil 22 and lamp 29 in multiple, conductor 26, resistance 2?, conductor 28, and conductor iii to the other side of the line. The time of the flash is controlled by the lamp 29, the tungsten filament of which increases in resistance as it is heated. When the switch 25 is first closed, the resistance of the cold filament of lamp 29 is comparatively low so that insufiicient current flows through the coil 22 of relay 2! to cause it to attract the armature 23. However, the filament in lamp 255 heats up very rapidly, thereby increasing in resistance so that sufiicient current flows through the coil 22 to cause it to attract the armature 23 and draw it away from the contact 32, thereby breaking the shunt circuit around the choke coil ill. The coil 22 holds the armature away from contact 32 until the switch 225 is opened, whereupon the spring 32' pulls the armature back against said contact 32 and the circuit is set to again flash the lamp it. The variable resistance 21 may be used to adjust the period of the flash between, for example, onesixtieth and one-fifth seconds.

The following characteristics were obtained with a lamp ll) of the high pressure mercury type described above: The lamp was rated at 100 watts and was connected through a reactor having an inductance of .157 henry to a 115 volt, 60 cycle line. The lamp operated normally at 65 volts and 1.65 amperes and produced a light intensity of 3,000 lumens. With the reactor shorted out, the lamp operated at 100 volts and 60 amperes and produced 400,000 lumens. The lamp was also operated from a 220 volt, 60 cycle line, a portion only of the ballast being shorted out in this case rather than the whole reactor. Under these conditions the lamp produced 3,100,000 lumens of light during the flash period.

temperature, the change in resistance The circuit shown in Fig. 2 is similar to that shown in Fig. 1 except that the ballast in this. case consists of a high reactance auto-transformer 4| and means are provided for flashing the lamp ill from a distance. The primary 42 of the transformer is connected across the line conductors I and H. The secondary 43 is connected at one side to the conductor l5 and at the other side to a conductor 44, said conductors l5 and 44 being connected to the upper and lower electrodes i2--l2 respectively of the lamp 10. The time control circuit 20 is connected in the same manner as in Fig. 1 except that armature switches 45 and 46 of a relay 4! have been substituted for the double pole switch 25. The coil of relay 41 is connected across the line leads i5 and II by conductors 48 and 49. When a push button 50 in conductor 49 is closed, the relay M is energized to close switches 45, 46, the transformer 41 being shunted momentarily to cause the lamp ID to flash at a high intensity.

In order to operate properly, the lamp it must be of suiiicient size and so constructed that the discharge therein is not extinguished by the increase in temperature and pressure therein during the period of the flash. The leads hi must be larger than in a lamp operated only under normal conditions so that they are not heated to such an extent as to crack the bulb of tne lamp at the seal. The electrodes l2--l2 must also be suiilciently large to withstand the abnormal current flow without damaging their activating properties. Furthermore, in some cases, as when operating on a 226 volt line, it is desirable to shunt only a portion of the ballasting device for the lamp it so that the lamp is not excessively overloaded. When using the device as a signalling means, the push button 50 in Fig. 2 may be replaced by a periodic circuit closing means, such as, a drum type switch or a cam switch, to cause the lamp to flash periodically. The lamp may also be electrically modulated, without the use of the time control means 20, to cause it to be flashed, for example, thirty times per second. The lamp must of course be suitably designed to withstand the frequent overloading.

What I claim as new and desire to secure by Letters Patent of the United States is:

The combination of an electric discharge lamp having a pair of electrodes, a ballasting device, said electrodes being connected through said ballasting device to a source of electrical energy for normal operation of the lamp, means for shunting out at least a portion of said ballasting device to permit an abnormal amount of current to flow through said lamp and produce a flash of light of high intensity, and time control means for automatically cutting out the said shunting means after a very brief interval of time to cause the said lamp to again operate under normal conditions, said time control means comprising I a circuit including a relay and resistance element rapidly with change in of said resistance element due to current passing therethrough causing said relay to be actuated to interrupt said shunting means.

whose resistance varies GEORGE E. INMAN. 

